Thioalkanal-s-oxides

ABSTRACT

This invention relates to novel thio-alkanal-S-oxides of the formula R=S=O wherein R is a straight-chain alkylidene group having from two to six carbon atoms. These novel compounds are useful to alter the flavor of consumable products. They may be prepared by reacting an alkyl sulfinyl chloride and a lower tertiary amine at a temperature below about -50* C.

United States Patent Brodnitz et al.

1 51 Aug. 22, 1972 THIOALKANAL-S-OXIDES [72] Inventors: Michael II. Brodnitz, Matawan;

John V. Pascale, Old Bridge; Manfred I-I. Vock, West Orange, all of NJ.

International Flavors & Fragrances Inc., New York, NY.

Filed: Feb. 24, 1970 Appl. No.: 13,816

Assignee:

US. Cl. ..260/607 R, 99/ 140, 260/453 R Int. Cl ..C07c 161/00 Field of Search "260/607 R, 607 C References Cited OTHER PUBLICATIONS Sheppard et al., J. Am. Chem. Soc., Vol. 86, pp. l,89I-2(l964) Opitz, Angewandte Chemie, Internation Ed., pp. 107- 9 Vol. 6 (1967).

. Primary Examiner-Joseph Rebold Assistant Examiner-D. R. Phillips Attorney-Brooks, Haidt & Haffner [5 7 ABSTRACT This invention relates to novel thio-alkanal-S-oxides of the formula R S 0 wherein R is a straight-chain 5 Claims, No Drawings THIOALKANAL-S-OXIDES BACKGROUND OF THE INVENTION This invention relates to products and processes for conferring fresh onion-like flavors on, and improving such flavors in, foodstuffs.

Considerable effort has been devoted to obtaining materials which can be added to foodstuffs for the purpose of providing pleasant flavors to foodstuffs. In many instances it is desirable to provide natural flavors to foods, and onions are a widely used natural material for improving or modifying the flavor of a wide variety of foodstuffs. Accordingly, there has been considerable interest in finding methods for simulating various aspects of onion flavor in foods.

Acta Chemica Scandinavica, 17, 641-650 (1963) describes attempts to isolate the so-called lachrymatory factor from natural onions. The lachrymatory factor was said to be (+)-S-(prop-1-enyl)-L-cysteine sulfoxide.

Cornell Experiment Station Memoir 385 stated that the structure which fitted their observations concerning the lachrymatory factor was thiopropional-S-oxide, although it was not isolated, and a possible precursor compound was suggested. In J.A.C.S. 86, 1891 (1964) an attempt was made to prepare thioaceton-S-oxide, but efforts to isolate this product were unavailing.

THE INVENTION Briefly, the present invention provides novel products and processes for improving the flavor and general organoleptic properties of foodstuffs. It has been found possible to prepare thioalkanal-S-oxides having the formula R S 0, where R represents an alkylidene radical having from two to six carbon atoms, by the reaction of alkyl sulfinyl halide with a tertiary amine. The compounds so obtained can be added to foodstuffs directly, or they can be permitted to undergo further rearrangement or reaction to provide a material having a fresh alliaceous flavor character. This material can also be added to food flavoring compositions or foodstuffs, as hereinafter more fully described. The alkylidene groups is desirably straight-chain, and preferred alkylidene groups include ethylidene, npropylidene, n-butylidene, n-hexylidene, and the like.

Thiopropanal-S-oxide obtained according to the present invention is a colorless liquid having a boiling point of 30 C at 0.10 mm Hg and a strong lachrymatory odor characteristic. The structure of this material is confirmed by proton magnetic resonance (PMR), gasliquid chromatography (GLC), and infrared (IR) and mass spectroscopy. If the substance is kept at room temperature (25 C) for two hours, it spontaneously reacts to form a material having a fresh onion odor and flavor, but if the substance is kept at C, it is stable for a period of at least 2 weeks.

Thiobutanal-S-oxide, CH CI-I -CI-l CI-I S O, is a liquid with a lachrymatory aroma. PMR spectroscopy confirms this structure.

Thiohexanal-S-oxide, CH CI-I --CH -CH CH -CH S 0, is a clear liquid boiling at 30 C under 0.3 mm Hg. Its PMR spectrum is consistent with the structure as aforesaid.

Thioethanal-S-oxide, Gil -CH S O, is a liquid with lachrymatory character, as are all of the thioalkanal-S-oxides prepared according to the present invention. Its structure is confirmed by PMR and mass spectroscopy.

The thioalkanal-S-oxides are prepared by reacting an alkyl sulfinyl halide with a tertiary amine. It is possible to prepare the thioalkanal-S-oxides at temperatures as high as room temperature, up to about 30 C, but after the product is formed further recovery, purification, and/0r isolation steps should be carried out at temperatures substantially below the freezing point of water, and more specifically, below about -1 5 C.

The reaction itself is desirably carried out at temperatures below -1 5 C in order to control the reaction and avoid the formation of unwanted by-products. At temperatures which are too low, the reaction will not proceed at a detectable rate, so it is desirable to carry out the reaction at temperatures above C. Accordingly, it is desirable to carry out the reaction at from 15 C to -80 C. It has been found that a good balance between yield, reaction time, and ease of production can be obtained in the preferred temperature range of from 15 to 30 C.

In order to moderate the course of the reaction and provide good contact between the reactants, it is desirable that the reaction be carried out in the presence of an inert reaction vehicle. Reaction vehicles for use in the present invention should be inert to and compatible with the reactants and should remain in a mobile liquid condition at the temperatures of reaction. They should also be readily separable from the S-oxide obtained according to the reaction. Reaction vehicles suitable for use in the practice of this invention include halogenated hydrocarbons such as carbon tetrachloride, trichlorofluoromethane, dichlorodifluoroethane, chlorotrifluoromethane,

dichlorotetrafluoroethane, carbon tetrachloride, and like materials; aromatic hydrocarbons such as benzene, toluene, xylene, and the like; aliphatic hydrocarbons such as pentane, hexane, isopentane, and the'like; alicyclic hydrocarbons such as cyclohexane and the like; and aliphatic ethers such as ethyl ether, methyl ethyl ether, methyl propyl ether, and the like.

It is desirable that the alkyl sulfinyl chloride be relatively pure, and purities of at least are preferred. The alkyl group of the starting material corresponds to the alkylidene group in the final S-oxide. Thus, propyl sulfinyl chloride provides propanal-S-oxide and so on. Such sulfinyl chloride starting materials can readily be obtained by conventional methods known in the art, e.g., the procedure set forth at Organic Syntheses, Vol. 40, pp. 6265 (1960).

It is desirable to combine the alkyl sulfinyl chloride and amine slowly so that adequate control of the reaction temperature can be maintained. In a preferred reaction procedure the amine is dispersed or dissolved in the reaction vehicle and the sulfinyl chloride is added until a stoichiometric or somewhat lower amount has been added. It is preferred that the molar ratio of chloride to amine be from 0.8/1 to 1.2/1. The reaction can be carried out under pressures which are above or below normal atmospheric pressure. Superatmospheric pressures are used with low-boiling vehicles, e.g., chlorotrifluoromethane, carbon tetrachloride, to suppress ebullition. It is generally preferred to carry out the reaction under normal atmospheric pressures.

Gaseous materials which would interfere with the course of the reaction should be excluded from contact with the reactants and the reaction vehicle. Accordingly, oxygen should be excluded from the reaction, and in this connection a blanket of insert gas such as nitrogen is preferably used.

The amines used in producing the S-oxides according to the invention are tertiary alkyl amines, which form onium ions. Thus, the structures contemplated include not only compounds of the formula N(R wherein R is a lower alkyl group having up to six carbon atoms and is preferably methyl or ethyl, but also cyclic tertiary amines having the formula wherein R is a lower alkylene group having up to four carbon atoms and is preferably a trialkylene diamine such as triethylene diamine. As used herein, tertiary amines will accordingly be taken to include such materials.

While thiopropanal-S-oxide or the other thioalkanal- S-oxides cannot long be maintained at room temperature, in one aspect of the present invention the material is permitted to stand at room temperature to form a product which has lost some or all of the lachrymatory character but which in turn provides a good fresh onion or other alliaceous flavor and aroma character. The product obtained upon standing of the S-oxide at room temperature or above is formed by rearrangement or further reaction of the S-oxide, and for convenience this will hereinafter be referred to as rearrangement. The rearrangement product is itself useful as a flavoring material in foodstuffs and flavoring compositions.

In the case of thiopropanaLS-oxide the rearrangement product forms upon exposure to temperatures above those at which the material is stable, as hereinbefore noted. Thus, the rearrangement product forms from the thiopropanal-S-oxide upon standing for 2 hours at 25 C or 30 minutes at 50 C. This rearrangement product has a strong fresh onion flavor. The rearrangement product from thiopropanal-S-oxide, for example, contains, in a ratio of 0.6:1 l, 3-pentenal, propyl propane thiosulfonate, and propyl propenyl thiosulfonate having the structure The compositions and products of the present invention can be used for providing onion flavor to foodstuffs including comestible liquids such as broths and other beverages. They can also be used to enhance, vary, alter, modify, fortify, and/or improve the flavors of foodstuffs. This invention is accordingly useful with foodstuffs such as soups and soup mixes, casserole dishes, canned and frozen meats and vegetables, animal and pet foods and other veterinary products, sauces, gravies, broths, stews, simulated meat and diary products, dietetic products, baked goods, and like products, as further described herein.

In accordance with a further of the present invention, the S-oxide or rearrangement product is utilized per se or in combination with other edible materials to impart the desired fresh onion organoleptic impression to foods or other edible materials. Thus, the mixtures herein described can comprise flavor compositions and flavor-enhancing compositions. It will be understood herein that a flavoring composition is one capable of imparting a definite, complete flavor to a tasteless or bland foodstuff, while a flavor-enhancing composition is one capable of reinforcing one or more flavor notes of a natural or other food material which is deficient in such flavor note.

A flavor-enhancing composition would be one useful for improving the flavor of, say, adehydrated onion product, the flavor of which had been diminished or altered undesirably by the dehydration and/or other processing. It will accordingly be understood that the products of this invention can be admixed with other flavoring ingredients, carriers, vehicles, and the like to form compositions suitable for imparting a flavor to, enhancing the flavor in, or altering the flavor of, a food composition, and such food compositions and the methods for preparing them are also contemplated herein.

When the materials of this invention are used in flavoring compositions to enhance existing flavors in, or to provide the entire flavor impression to, a foodstuff, the materials can be combined with organic acids including fatty, saturated, unsaturated, and amino acids, alcohols, including primary and secondary alcohols, esters, carbonyl compounds including aldehydes and ketones, lactones, cyclic organic materials including benzene derivatives, alicyclics, heterocyclics such as furans, pyridines, pyrazines, and'the like, other sulfur-containing materials including thiols, alkyl and alkylene monoand higher sulfides and the like, proteins, lipids, carbohydrates, and so-called flavor potentiators such as monosodiurn glutamate, and the like. It will be appreciated that the types and amounts of materials selected from the foregoing groups will depend upon the precise organoleptic character desired in the finished product and, especially in the case of flavoring compositions used to enhance other flavors, will vary according to the foodstufls to which the flavor and aroma are to be imparted. Inorganic materials such as sodium chloride, and freshness preservers such as:

butylated hdyroxyanisole, butylated hydroxytoluene, and propyl gallate can be added for their adjuvant or preservative effects on the flavoring compositions or upon the final food composition itself.

As noted above, it can also be desirable to utilize carriers or thickners such as gum arabic, carrageenen, gum tragacanth, guar gum and the like, or vehicles such as ethyl alcohol, water, propylene glycol, and the like. When the carrier comprises an emulsion, the flavoring composition can also contain emulsifiers such as sorbitol derivatives, monoand diglycerides of fatty acids, and the like. With these carriers or vehicles the desired physical form of the composition can be prepared. It will be understood that the mixtures of this invention can be used in spray-dried, liquid, encapsulated, emulsified, and other forms in which flavorings are added to foodstuffs. The mixtures can be so used alone or in combination with other ingredients set forth herein. It

will be understood that the mixtures of this invention can be utilized to provide or supplement onion flavors in sauces such as barbecue and spaghetti sauces, meats such as frozen hamburger patties, freeze-dried pork chops, and the like, soups, dried soup mixes, dehydrated soup mixes, and the like, gravies, salad dressings, spice mixes for preparation of, for example, vinegar-and-oil salad dressings, spreads such as butter or margarine, spreads for garlic bread, flavors for cottage cheese and other dairy products for salad use, cheese spreads, sour cream, cream cheese and other materials for use in dips, and the like.

The amount of the mixtures of this invention should be sufficient to impart the desired flavor and aroma qualities to the ultimate foodstuffs in which they are used. Thus, a small but effective amount of the mixture sufficient to provide the desired onion flavor note is used. The amount used will vary depending upon the ultimate food composition to be flavored; for example, more may be required in producing a full, rounded flavor from an unflavored material, and less may be required when the mixtures are used to enhance a natural product which is deficient in natural flavor or aroma.

Those skilled in the art will appreciate that the amount of the S-oxide or other material according to this invention can be varied over a range to provide the desired flavor and aroma. The use of too little of the mixture will not give the full benefit, while too much not only makes the flavor compositions and foodstuffs needlessly costly, but also can overwhelm and unbalance the flavor and aroma so that desirable results are not obtained. It is accordingly desirable that the ultimate food composition contain not more than 5 parts per million (ppm) of S-oxide or its rearrangement product for each part of total composition, and it is generally preferred to use more than about 0.002 ppm in the finished composition. Accordingly, the desirable range in foods of the materials produced according to this invention is from about 0.002 to 5 ppm. The generally preferred range of the thioalkanal-S-oxide or mixtures thereof is form 0.002 to 0.03 ppm.

When the S-oxide or reaction product is added to the foodstuff in the form of a total flavor composition, the amount should be sufficient to impart the requisite flavor and/or aroma note to the food composition so that the flavor and aroma will be balanced in the finished foodstuff. Accordingly, the flavoring compositions of this invention preferably contain from about percent to about 10- percent of the compound or compounds based upon the total weight of the flavoring composition. All parts, proportions, percentages, and ratios herein are by weight, unless otherwise specified.

The flavoring compositions of the present invention can be added to the foodstuffs by conventional means known in the art. The flavor material produced according to this invention, together with any other liquid if desired, can be admixed with a carrier such as gum arabic, gum tragacanth, carrageenen, and the like, and spray-dried to obtain a particulate solid flavoring material. When a powdered flavor mix is being made, the dried solids and mixtures of this invention are mixed together in a dry blender to obtain uniformity.

When liquid materials are involved in the preparation of foodstuffs, the flavoring materials of this invention can be combined with either the liquid to be used in the finished composition, or alternatively, they can be added with a liquid carrier in which they are dissolved, emulsified, or otherwise dispersed.

The following examples are given to illustrate embodiments of the invention as it is presently preferred to practice it. It will be understood that these examples are illustrative, and the invention is not to be considered as restricted thereto except as indicated in the appended claims.

EXAMPLE 1 Synthesis of Thiopropanal-S-Oxide A 100 ml three-neck flask provided with a dropping funnel, magnetic stirrer, and a nitrogen blanket is charged with 10.1 g (0.1 mole) of triethylamine and 60 ml of carbon tetrachloride. The compounds are cooled to 20 C using a dry ice-isopropanol bath, and 12.65 g (0.1 mole) of propyl sulfinyl chloride cooled to 0 C is slowly added to the flask. The temperature during addition is maintained between 20 and -25 C, and a precipitate forms in the mixture.

After addition is completed, the reaction mixture is filtered through a coarse sintered glass filter into a precooled suction flask. The filtrate is filtered twice utilizing filter paper and suction. A sample of the carbon tetrachloride solution is subjected to IR spectroscopy which indicates that the product is thiopropanal-S-oxide. This is confirmed by a mass spectral analysis showing a parent peak at and two other prominent peaks at 73 and 45. PMR at 20 C confirms the structure by showing a doublet at 1.40 ppm, a multiplet at 8.40, and a triplet at 10.00.

Upon standing seventeen hours at room temperature 25 C or for 30 minutes at 50 C, the product breaks down to form a substance having a fresh onion flavor character.

EXAMPLE II A 500 ml three-necked round-bottom flask equipped with a mechanical stirrer, thermometer, dropping funnel and nitrogen blanket is charged with 20.1100 g (0.199 mole) of triethylamine and dissolved in trichlorofluoromethane. The solution is cooled to 20 to -40 C with a dry ice-isopropanol bath, and 25.3027 g (0.199 mole) of propane sulfinyl chloride is added dropwise to cooled reaction mixture. The reaction mixture is stirred at 40 to 20 C for 1 hour after the addition has been completed.

The reaction mixture is then placed in a rotary evaporator and the trichlorofluoromethane is removed under mm Hg pressure to obtain a solid-liquid mixture. The mixture is transferred to stainless steel centrifuge tubes by using trichlorofluoromethane, and the tubes are centrifuged at 20 C for 1 hour. The solution is filtered, and the filter is placed on the rotary evaporator to remove the trichlorofluoromethane at 90 mm Hg pressure.

This provides 12.5 g of thiopropanal-S-oxide which is a colorless liquid boiling at 30 C at 0.10 mm Hg. PMR analysis in deuterotrichloromethane shows the followmg:

Chemical Shift Coupling Integral Assignment (5; ppm) C nstant (J) Ratio 2.75 2 -Cfl,-CH S 1.18 (triplet) Hz 3 CH, -c-c= 1.39 6 CH,(Cfl,),-CH, 2.80 (quintet) 7 Hz 2 QH, c CH s o 8.14 (triplet) 7 Hz 1 RC o 0.89 3 c%, cil,), cii s A signal noted at 1.60 ppm is due to an impurity in the deuterotrichloromethane.

Similar results are obtained when the foregoing reac- The thlohexanal's'oxlde Produced 15 Useful In tion is carried out with other halogenated hydrocarenhancing meat flavorsbons such as tetrafluoromethane, dibromodichloromethane and the like, aromatic 10 EXAMPLE hydrocarbons such as toluene, xylene and benzene; A 250 ml flask fitted with a thermometer, dry ice aliphatic hydrocarbons such as butane, pentane, hexn n r, ag a pp g un is arg ane; and the like. Similarly, other lower tertiary 211- with 10.1 g (0.10 moles) of triethylamine in 100 cc of kylamines such as trimethylamine, t ipro l mi fluorotrichloromethane, and.l3.9 g of propyl sulfinyl tributylamine, triethylenediamine, and the like can b chloride is added dropwise over a five-minute period used. while the temperature is maintained at 22 to 30 C. The thiopropanal-S-oxide and/or its rearrangement When the addition is complete, the precipitate is product improves the overall taste of roasted meat removed by vacuum filtration, the filtrate is charged to products, whether pure or combined with otei f m a rotary evaporator, and the fluorotrichloromethane is other sources such as vegetable, fish, single-cell life removed at 90mmHg pre s ref rm and th lik at usage l l f 002..0 03 ppm The solid-liquid mixture obtained from the evapora- At the lowest usage levels, the novel product of this in- 15 centrifuged for One hour at the Solids are ti t as an enhancer, hil at hi h l l separated by filtration, and the fluorotrichloromethane characteristic alliaceous flavor character is perceived. is removed on the rotary evaporator at 90 mm 8- No The product is also suitable for use as a flavor in- 25 heat is added in h evaporation p gredient in related alliaceous flavors, such as chive, The Procedure yields gofthiopropana-l's-oxidescallion, garlic, leek, and the like, and in such usage, levels of 0.1 ppm of the finished product provide good EXAMPLE VIII results. The product of Example II is dissolved in 95 percent ethanol to provide a 2 percent solution, and is held at EXAMPLE room temperature for 24 hours. It is then diluted with h process f Example 11 is repeated utilizing 2733 water to 0.01 percent, and this solution has an aroma of g (2.2 moles) of propyl sulfinyl chloride and 20.22 g fresh green onlons- (20 moles) of triethylamine. The yield ofproduct is 17 Vanous water solutions are prepared, as shown in g, or about 945 percent the following Table I and evaluated for taste:

EXAMPLE IV TABLEI Synthesis of Thiobutanal s oxide Concentration (ppm) Evaluation The procedure of Example II is repeated utilizing 0002 Green onion charamnnem 20.22 g (0.20 moles) of triethylamine and 30.9 g (0.22 threshold level moles) of butyl sulfinyl chloride. The procedure Fresh produces 17.1 g of thiobutanal-S-oxide having a 12:25: i g ggg l and mass Spectral analysls The material is added to chicken broth to obtain a concentration of 0.010 ppm, and it is found that the EXAMPLE V chicken taste is deepened and that a light onion aftertaste is added. Increasing the concentration to 0.030 Synthesls of Thoethanal'soxlde ppm adds an onion aroma, and the fresh onion taste is The procedure of Example 11 is repeated with the dominating same molar quantities of ethyl sulfinyl chloride. PMR ev 9 the foregomg wlth beef broth shows no and mass spectral analysis confirm the structure of the slgmficam dlfiemnce at 9- p 3 sllghfly thi fll s id produced lachryrnatory aroma and an improved general taste at 0.030 ppm; and a dominating onion note with the beef EXAMPLE VI broth changed to onion soup at 0.2 ppm. It is 'ud ed that this flavor additive can re lace all Synthesls of Thlohexanal's'oxlde flavor a reai where fresh onionis used, and it is interest- Per the procedure of Example II, 25.3 g (0.15 moles) ing enough to be used alone to develop onion soup of hexyl sulfinyl chloride is reacted with 16.2 g (0.16 flavor chafactellstlcmoles) of triethylamine in 250 ml of fluorotrichloromethane to produce 21 g of thiohex- EXAMPLE IX anal-S-oxide boiling at 30 C under 0.3 mm Hg. PMR Three meat-loaf type products are prepared accordanalysis shows the following: ing to the following formulation:

Shift (ppm) No. of Protons Assignment Ingredient Amount 8.13 1 --CE S O TVP, minced 1 cup Ground beef 1 cup Water 1 cup Beef suet Vs cup Bread crumbs, dry, unflavored 1 cup Whole milk 1 cup Egg albumen 3 tbsp. Salt 1% tbs Black pepper V4 teasp. Catsup A cup Water 32 ml.

The TVP is a texturized vegetable protein mixture made by Archer-Daniels-Midland Company.

Three separate portions prepared according to the foregoing formulation are made into three meat loaves. Loaf A contains no additional additive, Loaf B contains 32 ml of fresh pressed onion juice to replace the 32 ml of water, and Loaf C contains 0.6 ppm of the rearrangement product produced in Example II.

The three loaves are baked at 350 F for 1 hour and evaluated for flavor by a panel of twelve judges. The consensus of the judges is that Loaves B and C are superior to Loaf A because the onion character of B and C enhances the overall taste and covers the dry, cardboard-like cereal character of Loaf A. It is accordingly apparent that the product of this invention is a valuable ingredient for a wide variety of flavors and types of foodstuffs.

What is claimed is:

1. A thioalkanal-S-oxide having the formula according to claim 1 according to claim 1 according to claim 1 according to claim 1 

2. A thioalkanal-S-oxide according to claim 1 wherein R is ethylidene.
 3. A thioalkanal-S-oxide according to claim 1 wherein R is propylidene.
 4. A thioalkanal-S-oxide according to claim 1 wherein R is butylidene.
 5. A thioalkanal-S-oxide according to claim 1 wherein R is hexylidene. 